Art of setting diamonds



March 8, 1%32. c, J, KOEBEL 1,848,182

ART OF SETTING DIAMONDS Filed June 20, 1950 Fatented Mar. 8, 1932 GEAR-LES J. KOEBEI, OF DMBOIT, MIGHIGAN, ASSIGNOB T KOEBEL-WAGNEB DIAMOND GORP, OF NEWARK, NEW m, A CORPORATION OF DELAWARE ART OF SETIING DIAMONDS Application filed June so, 1930. Serial m. 462,4.

This invention relates generally to the art of setting diamonds, carbonados or the like, especially for industrial purposes.

Diamonds are now being used to a very great extent in the industrial arts, examples of such use being: as dressing tools for grinding wheels; as core bits for rock drilling; as saw teeth; and as dies for drawing wire.

Manifestly their use for such purposes as have been indicated above, imposes strains and stresses of considerable magnitude upon the diamonds and their mounting. Unless the diamond is held very firmly in its mounting, it may work loose and become lost or, if not lost, it will quickly destroy its own setting and will become useless asa tool. It is the practice now to use relatively large stones and to reset them when they work loose. Bepeated resettings however, especially if heat 29 be used, have a very deleterious efi'ect upon the diamond, and it is therefore not always possible to reset a diamond as it may have become injured or its skin may have been destroyed or penetrated, by adjacently mounted diamonds or otherwise, to such an extent that it is no longer serviceable in the task for which it is intended.

It is the main object and feature of this invention to so set diamonds or the like that they will be firmly held under most exacting conditions, that they will not be injured during the process of setting them although subjected to heat during such process, and that stones of smaller size than those heretofore as employed can now be used to advantage with a consequent enormous reduction in the cost of the tool.

It has been found that the above advantages can be obtained by proceeding as follows:

The diamond or diamonds are imbedded in a mass of comminuted alloy of such character that, when subjected to heat at a point below the critical point at which the desirable that the alloy, when heated, exhibits the property of wetting the diamond coupled with a. lack of avidity for the carbon of the diamond and, when thereafter cooled, of closely adhering to it. The mass of alloy, in which the diamond has been positioned, is formed, by subjecting it to pressure, into a shaped body capable of substantially maintaming its form when pressure is thereafter removed. lt has been round that a pressure of from thirty to forty tons to the square inch is suitable for this purpose, and this pressure may be left on for a short interval, if desired, say one minute. lf more than one diamond is to be imbedded in the alloy, it is important that the diamonds be properly positioned and spaced and that enough powder or comminuted material is placed between them so that, when'the alloy 18 sub jected to the pressure above described and to the shrinkage to be presently described, the stones will not come in contact with each other. The shaped body thus produced is capable of maintaining its shape if carefully handled, and it is then placed in am open vessel or on a suitablesupport which latter, in turn, is introduced into a furnace or heating chamber where the body is subjected to a temperature lower than the critical point at which the desirable qualities of the diamond are impaired but sufliciently high to set and somewhat shrink, or to sinter, the body into a coherent product. The critical point above mentioned appears to be in most cases I in the neighborhood of 1380 degrees centigrade, although it varies with difi'erent stones. Excellent results have have been obtained by using a temperature between 1245 and 1260 degrees centigrade. The furnace is provided with hydrogen flame curtains at its entrance and exit ends, and the jets that furnish the hydrogen flame are lighted before the shaped body is introduced into the furnace so as to render the latter devoid of oxygen. The furnace may be brought up to substantially the required heat before the shaped body is introduced therein, and said body need remain only long enough in the furnace to admit of the required'temperature being reached. If desired, there may be a preliminary heating of the shaped body in another furnace,.also devoid of oxygen, and good results have been obtained with a preliminary heating of 400 degrees centigrade. After the shaped body has been sufiiciently heated, in the present instance between 1245 and 1260 degrees centigrade, the vessel containing it is introduced into a cooling chamber, conveniently located at the exit end of the furnace, said cooling chamber being also provided with hydrogen flame curtains to exclude oxygen. The product is now cooled down preferably to substantially normal temperature, that is, cool enough to be taken with the bare hand. The product has shrunk but slightly but has become a coherent solid mass in which the diamonds are firmly imbedded in the same relative position they originally occupied, and it would therefore seem that the effective coefficient of expansion of the alloy approximates that of the diamond. Any surplus material that covers the diamonds may now be removed by machinery, by sandblasting or otherwise and the product may then be fitted into a suitable holder or support.

By way of example, but not of limitation, the following formula of an alloy, successfully used, is given:

Per cent Molybdenum 26 Cobalt 46 Copper 27.75 Iron 00.25

The proportions given are by weight and not by volume. The materials of which the alloy is composed are reduced to powder form and thoroughly mixed, a slight amount of paraffin being added, before the diamond is imbedded therein. Molybdenum is chosen because, apparently, it imparts a hardness of high degree to the finished setting. The function of the cobalt appears to be that of rendering the alloy wettable with respect to the diamond. The copper seems to prevent the alloy from robbing the diamond of carbon. 1

In addition to the advantages to be obtained by this invention already referred to, it may be pointed out here that, by the described process, the diamond makes its own socket or recess, and this socket necessarily conforms in every detail to the shape of the stone no matter how irregular. In other words, all the advantages of a setting made from molten metal is obtained, with none of the disadvantages, such as the shock caused by impingement of molten metal on the skin of the diamond. Furthermore, the alloy used, unlike molten steel for instance, does not become carburized by contact with the diamond, nor is the diamond subject to oxidation which so readily takes place when a diamond is heated in the presence of oxygen. The advantage over the type of setting in which metal is swaged or peened over the equator of the stone will likewise be apparent, because, obviously, there never can be the intimate contact between the stone and the setting produced by the peening process that there exists in the setting produced by the herein described process. Lack of such intimate contact not only results in-imperfcct holding of the stone but also reduces the heat conducting qualities of the setting, a very important factor in diamond tools used for industrial purposes because obviously, in'the use of such tools, considerable heat is generated and the stone should be relieved of the effects of the generation of such heat as much as possible.

In the accompanying drawings, a preferred form of apparatus for practicing the invention is disclosed. It will be understood, however, that such apparatus is shown by way of illustration and not of limitation.

In said drawings:

Figs. 1, 2 and 3 are diagrammatic views, in section, showing the molding steps;

Fig. 4 is a diagrammatic View, in section, showing the furnace that may be employed in carrying out the invention; and

Fig. 5 shows a finished product that may be obtained by the invention.

The particular product here desired, and

' used by way of illustration, is a core bit for a rock drill. Said core bit is indicated at 1 in Fig. 5 and is a cylindrical and tubularmember having diamonds 2 imbedded at such suitable points as may be desired. In Figs. 1 to 3, a mold 3 is illustrated which may be used in connection with the process of the invention. Said mold here consists of a lower plate member 4 and cylindrical sidewalls 5. 6 is a centrally disposed core member and 7 is a piston or-plunger wherewith to exert pressure. The comminuted alloy 8 and the diamonds 9 are placed in the mold around the core member, care being taken to position the diamonds in the relative position it is desired to have them occupy, and sufficient powder being placed around each diamond to render it certain that the stones, in the finished product, will not come in contact with each other. Plunger 7 now descends and compresses the mass as indicated diagrammatically in Fig. 2 whereby a shaped body 10 is produced. The shaped body is now removed from the mold and placed on a carbon support or open vessel 11 which is introduced into furnace 12. The particular furnace here shown has a heating chamber 13, an entrance chamber 14 and a cooling chamber 15. 16 indicates a gate to the entrance chamber and this gate has a ventilating door 17. The furnace chamber consists ofa porous tube 19 en-- circled by an electric heating coil 20, there 'being a porous insulation 21 provided to Theexit or cooling chamber is provided with a water jacket 23 having suitable inlet and outlet pipes 24. 25 indicates an outlet gate adjacent which there is a hydrogen burner 26. Before the shaped body is introduced into the furnace, the current is turned on and the hydrogen burners are lit, the gates being closed, so that all oxygen is consumed. The ventilating door, however, remains open and the hydrogen flame extends from one end of the furnace to the other. This flame is not intensive and is not used for heating purposes but merely for the purpose of excluding oxygen. The entrance gate is now opened and the shaped body is introduced into and remains in the furnace until the proper temperature has been reached, after which said body is moved into the cooling chamber. The current may or may not then be turned off but the hydrogen burners at the inlet and outlet gates are still kept burning to exclude oxygen. After the shaped body has been suiticiently cooled, it is removed from the cooling chamber. If desired, the process may be a continuous one, a number of vessels being at different positions in the furnace.

The alloy per 'se is not claimed herein but forms the subject matter of another application filed January 12, 1932, Ser. No. 586,238.

I claim:

1. The process of setting diamonds or the like, which consists in positioning the diamond in a mass of comminuted alloy, composed of base metals, which alloy when heated exhibits the property of wetting the diamond coupled with a lack of avidity for the carbon thereof and, when thereafter cooled, of closely adhering to it, then forming said mass of alloy, by subjecting it to pressure, into a shaped body capable of substantially maintaining its form when pressure is thereafter removed, then removing the pressure from said body, and then subjecting the shaped body to a temperature that is below the critical point at which the desirable qualities of the diamond are impaired but sufiiciently high to set and somewhat shrink said body into a coherent product that firmly and uniformly engages the diamond and that retains it substantially in its predetermined position in the mass.

2. The process of setting diamonds or the like, which consists in positioning the diamond in a mass of comminuted alloy, composed of base metals, which alloy when heated exhibits the property of wetting the diamond coupled with a lack of avidity for the carbon thereof and, when thereafter cooled, of close- 1y adhering to it, then forming said mass of alloy, by subjecting it to pressure, into a shaped body capable of substantially maintaining its form when pressure is thereafter removed, then removing the pressure from said body, and then subjecting the shaped body, in a furnace from which oxygen is excluded, to.a temperature that is below the critical point at which the desirable qualities of the diamond are impaired but sufiiciently high to set and somewhat shrink said body into a coherent product that firmly and uniformly engages the diamond and that retains 1t substantially in its predetermined po-' sition in the mass. I

3. The process of setting diamonds or the like, which consists in positioning the diamond in a mass of comminuted alloy, including molybdenum, copper and cobalt, then forming said mass of alloy, by subjecting it to pressure,-into a shaped body capable or substantially maintaining its form when pressure is thereafter removed, then removing the pressure from said body, and then subjecting the shaped body to a temperature that is below the critical point at which the desirable qualities of the diamond are irnpaired but sufiiciently high to set and somewhat shrink said body into a coherent prodnot that firmly and uniformly engages the diamond and that retains it substantially in its predetermined position in the mass.

1. The process of setting diamonds or the like, which consists in positioning the diamond in a mass of comminuted alloy, including molybdenum, copper and cobalt, then forming said mass of alloy, by subjecting it to pressure, into a shaped body capable of substantially maintaining its form when pressure is thereafter removed, then removing the pressure from said body and then subjectmg the shaped body, in a furnace from which oxygen is excluded, to a temperature that is below the critical point at which the desirable qualities of the diamond are impaired but sufiiciently high to set and somewhat shrink said body into a coherent product that firmly and uniformly engages the diamond and that retains it substantially in its predetermined position in the mass.

5. The process of setting diamonds or the like, which consists in imbedding the diamond in a mass of comminuted alloy, which alloy when heated exhibits the property of wetting the diamond coupled with a lack of avidity for the carbon thereof and, when thereafter cooled, of closely adhering to it,

' and then subjecting the mass to a temperature that is below the critical point at which the desirable ualities of the diamond are impaired but su ciently high to sinter the mass into a coherent product.

Si ned at Detroit, in the county of Wayne, and tate of Michigan, this 13th day of June,

CHARLES J. KOEBEL. 

